<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <script src="https://unpkg.com/vue/dist/vue.js"></script>
    <script src="https://unpkg.com/vue-router/dist/vue-router.js"></script>
    <title>Title</title>
</head>
<body>


<div id="app">
    <p>
        <router-link to="/user/foo">/user/foo</router-link>
        <router-link to="/user/foo/profile">/user/foo/profile</router-link>
        <router-link to="/user/foo/posts">/user/foo/posts</router-link>
    </p>
    <router-view></router-view>
</div>
</body>
</html>
<script>
    const User = {
        template: `
            <div class="user">
                <h2>User {{ $route.params.id }}</h2>
                <router-view></router-view>
            </div>
        `
    };

    const UserHome = { template: '<div>Home</div>' }
    const UserProfile = { template: '<div>Profile</div>' }
    const UserPosts = { template: '<div>Posts</div>' }

    const router = new VueRouter({
        routes: [
            { path: '/user/:id', component: User,
                children: [
                    { path: '', component: UserHome },
                    { path: 'profile', component: UserProfile },
                    { path: 'posts', component: UserPosts }
                ]
            }
        ]
    })

    const app = new Vue({ router }).$mount('#app')
</script>